BOSTON -- When Mom eats fish during pregnancy, junior may get a developmental boost.

Action Points

Explain to patients that this study suggests that increased fish consumption during pregnancy may aid child development during the first 18 months of life.

Note that the findings came from a retrospective review of a large database, not a randomized, controlled clinical trial, and do not prove causality.

BOSTON, Sept. 12 -- When Mom eats fish during pregnancy, junior may get a developmental boost.

Maternal fish intake averaging about 59 g a day (2 oz.) was associated with significantly higher development scores for the infant at 18 months compared with scores of children whose mothers consumed an average of only 5.4 g a day, Emily Oken, M.D., of Harvard, and colleagues reported in the September issue of the AmericanJournal of Clinical Nutrition.

The researchers also found that, consistent with previous studies, longer duration of breastfeeding correlated with better developmental scores.

Fish consumption did not have an additive effect to the benefits of breastfeeding.

"The effects of maternal prenatal fish consumption and breastfeeding duration were independent of each other," the authors said. "Contrary to our hypothesis, the benefit of maternal fish intake was not greater in the children breastfed for a shorter duration."

Accumulating evidence suggests that early nutrition influences the neurodevelopment of infants. Considerable interest in the association has focused on maternal intake of the long-chain n-3 polyunsaturated fatty acid docosahexaenoic acid, an essential structural component of brain tissue, the authors said.

The primary dietary source of docosahexaenoic acid is fish and seafood.

However, few studies have examined the effects on child development of maternal consumption of n-3 fatty acid during pregnancy, they continued.

The Danish National Birth Cohort, a prospective population-based study, provided an opportunity to examine those potential associations. The study included pregnant women enrolled during 1997 to 2002. Participants in the study provided information about maternal nutrition, breastfeeding, pregnancy characteristics, and other aspects of the prenatal and early infancy periods.

Information about infant development came from standardized interviews with mothers at six and 18 months postpartum. The data were used to generate developmental scores for the 25,446 children born to the study participants.

The primary outcome was total child development at 18 months, determined from mothers' answers to nine questions related to developmental milestones (such as the child's ability to climb stairs, drink from a cup, and use word-like sounds).

The mothers were grouped into tertiles according to average self-reported fish consumption: 5.4 g/day, 22.3 g/day, and 58.6 g/day.

Additionally, breastfeeding duration of 10 months or more predicted higher 18-month developmental scores than breastfeeding of one month or less (OR 1.28, 95% CI 1.18 to 1.38). Associations of fish intake with child development did not differ by breastfeeding duration.

The authors noted that authorities on prenatal nutrition in the United States and Europe have recommended that pregnant women consume a minimum of 200 mg of docosahexaenoic acid daily.

Because most women to not consume enough fish and other dietary sources to meet that recommendation, they suggested that supplements might be a reasonable alternative.

But, because fish consumption involves some risk of exposure to contaminants, particularly organic mercury, advisory groups in the U.S. have recommended that pregnant women limit intake of seafood to 340 g a week.

Acknowledging that concern, the researchers nonetheless said "the results from the present study do not show any oral detrimental effect of prenatal fish intake on developmental milestones, but, rather they show that higher maternal fish intake is associated with better early development."

"Thus, for the amount and type of fish intake observed in this population, the nutrient benefits of prenatal fish intake for child development appear to outweigh the toxicant harms," they said.

However, they did recommend that "to maximize the benefits and minimize the risks, [pregnant women] consider toxicant concentrations in choosing fish to consume."

Co-author Matthew Gillman has received grant support from MeadJohnson Nutritionals. Co-author David Bellinger served on a panel supported by the National Food Producers Association.

Reviewed by Robert Jasmer, MD Associate Clinical Professor of Medicine, University of California, San Francisco